Re: [TANKS] Remote Triggering - R/C MOSFET switch works fine

[Mike Lyons]

In 4.1 I am describing a microprocessor or something similar that produces 
true high and low logic levels.
I'm *not* referring to an ordinary R/C receiver.

The logic-level device may have interpreted R/C signals and produced a 
different type of output,
or it might be a non-R/C solution (WiFi, Bluetooth, etc).


On Wednesday, October 8, 2014 9:37:27 PM UTC-4, True North Armouries wrote:
>
> 4.1 the problem is that the output from the receiver is not a digital 
> logic signal in the high/low sense of the word. Its a ~50hz signal who's 
> duty cycle varies with the position of the stick. Hence why you need a 
> servo switch. 
>
...

>  

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Re: [TANKS] Remote Triggering - R/C MOSFET switch works fine

[isaac goldman]

4.1 the problem is that the output from the receiver is not a digital logic
signal in the high/low sense of the word. Its a ~50hz signal who's duty
cycle varies with the position of the stick. Hence why you need a servo
switch.

Thanks for clarifying that Frank. For some reason I thought you meant a MAG
style switch to energise the FET.

I dont trust opto-isolators to handle the spike from an inductive load like
a solenoid. Replacing the e-trigger with one could work, but directly
energising the solenoid off it doesnt appeal to me.



On Wed, Oct 8, 2014 at 6:24 PM, Frank Pittelli 
wrote:

> There always has to be some sort of electronic interface between the R/C
> Receiver and the door-lock (or e-trigger) solenoid and Mike has been
> cataloging the various ways that can be done.
>
> Option (a) below is the simplest solution, that anyone can implement with
> only basic tools and wiring skills.  It can also be done for less than $5
> using readily available parts from surplus catalogs.  It also doesn't
> require any modifications to the marker.
>
> Options (b), (c) and (d) below don't use a "servo", they use a "servo
> switch" which is "an electronic circuit that accepts a servo input signal
> and then switches something".  The most common servo switch circuits use a
> simple micro-processor to read the servo signal and trigger the switch.
> Old-timers used a 555 and an assortment of other components to achieve the
> same goal but that's horse-and-buggy type stuff.
>
> Mike listed some servo switches that are commercially available, all of
> which can be used to operate a door-lock actuator or switch an e-trigger
> circuit.  When used with a door-lock actuator, no marker modifications are
> required.  When used with the e-trigger mechanical switch, you need only
> solder a pair of wires between the mechanical switch and the servo switch.
>
> Option (d) is a prototype circuit board used in the most recent battles
> that can drive the e-trigger solenoid directly from a servo signal.  It
> requires the most drastic changes to the marker, disconnecting the solenoid
> from the e-trigger circuit and connecting it to the servo switch board.
>
> I guess we should also include an Option (e) which is an
> "Opto-isolator-based Servo Switch".  They provide isolation like a
> mechanical relay without any moving parts, but they can't handle as much
> current as a FET or relay.  Relays, FETs and opto-isolators are the most
> common approaches for switching something, with various advantages and
> disadvantages that keep them all in use.
>
> On 10/8/2014 5:17 PM, isaac goldman wrote:
>
>> Why does there have to be a servo involved? You can fire a door lock
>> solenoid with only electronics quite easily. Or am i misunderstanding?
>>
>> Ill post a circuit later tonight.
>>
>> On 2014-10-08 5:12 PM, "Frank Pittelli" > > wrote:
>>
>> a) Servo & Mechanical Switch
>> b) Relay-based Servo Switch
>> c) FET-based Servo Switch
>> d) Prototype CCS Servo Switch (FET-based)
>>
>
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Re: [TANKS] Remote Triggering - R/C MOSFET switch works fine

[Frank Pittelli]

There always has to be some sort of electronic interface between the R/C 
Receiver and the door-lock (or e-trigger) solenoid and Mike has been 
cataloging the various ways that can be done.


Option (a) below is the simplest solution, that anyone can implement 
with only basic tools and wiring skills.  It can also be done for less 
than $5 using readily available parts from surplus catalogs.  It also 
doesn't require any modifications to the marker.


Options (b), (c) and (d) below don't use a "servo", they use a "servo 
switch" which is "an electronic circuit that accepts a servo input 
signal and then switches something".  The most common servo switch 
circuits use a simple micro-processor to read the servo signal and 
trigger the switch.  Old-timers used a 555 and an assortment of other 
components to achieve the same goal but that's horse-and-buggy type stuff.


Mike listed some servo switches that are commercially available, all of 
which can be used to operate a door-lock actuator or switch an e-trigger 
circuit.  When used with a door-lock actuator, no marker modifications 
are required.  When used with the e-trigger mechanical switch, you need 
only solder a pair of wires between the mechanical switch and the servo 
switch.


Option (d) is a prototype circuit board used in the most recent battles 
that can drive the e-trigger solenoid directly from a servo signal.  It 
requires the most drastic changes to the marker, disconnecting the 
solenoid from the e-trigger circuit and connecting it to the servo 
switch board.


I guess we should also include an Option (e) which is an 
"Opto-isolator-based Servo Switch".  They provide isolation like a 
mechanical relay without any moving parts, but they can't handle as much 
current as a FET or relay.  Relays, FETs and opto-isolators are the most 
common approaches for switching something, with various advantages and 
disadvantages that keep them all in use.


On 10/8/2014 5:17 PM, isaac goldman wrote:

Why does there have to be a servo involved? You can fire a door lock
solenoid with only electronics quite easily. Or am i misunderstanding?

Ill post a circuit later tonight.

On 2014-10-08 5:12 PM, "Frank Pittelli" mailto:frank.pitte...@gmail.com>> wrote:

a) Servo & Mechanical Switch
b) Relay-based Servo Switch
c) FET-based Servo Switch
d) Prototype CCS Servo Switch (FET-based)


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Re: [TANKS] Remote Triggering - R/C MOSFET switch works fine

[Mike Lyons]

Very interesting.  Thanks, Frank!

This suggests an even simpler and lower-cost solution:

4.1  Connect the output of a logic-level device (examples in 4 above) to 
the high side of the trigger,
and the ground of the device to the marker ground (the low side of the 
trigger would be convenient).

The logic levels don't matter as long as "high" is high enough that the 
marker doesn't interpret it as "low" and not so high that it blows 
something (unlikely),
and "low" is ground level.



On Wednesday, October 8, 2014 2:38:02 PM UTC-4, Frank Pittelli wrote:
>
> The switch on the e-trigger is a standard active-low input to 
> a micro-processor I/O port 

...

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Re: [TANKS] Remote Triggering - R/C MOSFET switch works fine

[isaac goldman]

Why does there have to be a servo involved? You can fire a door lock
solenoid with only electronics quite easily. Or am i misunderstanding?

Ill post a circuit later tonight.
On 2014-10-08 5:12 PM, "Frank Pittelli"  wrote:

> Usually, the door lock actuator is used for manual triggers, because it
> pulls harder and faster than a servo by itself.  When an e-trigger is used,
> very little force is needed, so the door lock actuator is not really
> needed.  Nonetheless, any of the following configurations could be used to
> activate a door lock actuator with proper wiring:
>
> a) Servo & Mechanical Switch
> b) Relay-based Servo Switch
> c) FET-based Servo Switch
> d) Prototype CCS Servo Switch (FET-based)
>
>
> On 10/8/2014 3:53 PM, Mike Lyons wrote:
>
>> What's the interface between the R/C receiver (or equivalent e.g. C12C
>> plug plug plug) and the door lock thingamy?
>>
>
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Re: [TANKS] Remote Triggering - R/C MOSFET switch works fine

[Frank Pittelli]

Usually, the door lock actuator is used for manual triggers, because it 
pulls harder and faster than a servo by itself.  When an e-trigger is 
used, very little force is needed, so the door lock actuator is not 
really needed.  Nonetheless, any of the following configurations could 
be used to activate a door lock actuator with proper wiring:


a) Servo & Mechanical Switch
b) Relay-based Servo Switch
c) FET-based Servo Switch
d) Prototype CCS Servo Switch (FET-based)


On 10/8/2014 3:53 PM, Mike Lyons wrote:

What's the interface between the R/C receiver (or equivalent e.g. C12C
plug plug plug) and the door lock thingamy?


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Re: [TANKS] Remote Triggering - R/C MOSFET switch works fine

[Mike Lyons]

My crystal ball is a little fuzzy but I think I see "CRCS".


On Wednesday, October 8, 2014 2:38:02 PM UTC-4, Frank Pittelli wrote:
>
> ... 

6) Use a prototype Cheap Control Systems Servo Switch board to drive the 

solenoid directly 

 ...

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Re: [TANKS] Remote Triggering - R/C MOSFET switch works fine

[Mike Lyons]

What's the interface between the R/C receiver (or equivalent e.g. C12C plug 
plug plug)
and the door lock thingamy?


On Wednesday, October 8, 2014 2:38:02 PM UTC-4, Frank Pittelli wrote:
>
> ... 

5) Use a door-lock actuator to pull the manual trigger. 

...

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Re: [TANKS] Remote Triggering - R/C MOSFET switch works fine

[Frank Pittelli]

The switch on the e-trigger is a standard active-low input to a 
micro-processor I/O port, which is why the current is so low.  The 
micro-processor then combines the input with the current operating state 
(e.g., firing mode, trigger lock-out, etc) and, if firing is warranted, 
activates a FET on the e-trigger board to provide power to the solenoid 
for no more than 5 ms.  The short burst is sufficient to trip the 
mechanical sear, but not long enough to draw a lot of current from the 
9V transistor battery that powers the e-trigger board.  A large 
capacitor recharges the firing circuit in just a few milliseconds after 
it is fired.


You left out two other options for firing an e-trigger:

5) Use a door-lock actuator to pull the manual trigger.

6) Use a prototype Cheap Control Systems Servo Switch board to drive the 
solenoid directly, thereby completely replacing the mechanical trigger, 
mechanical switch, e-trigger board and the 9V transistor battery. 
Battle Tested. Tri-Pact Approved.


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[TANKS] Remote Triggering - R/C MOSFET switch works fine

[Mike Lyons]

I finally found the time and motivation to test the Pololu RC Switch with 
Small Low-Side MOSFET 
It works as expected.  Bazooka Joe is now a little more bionic (strictly 
speaking he's more electronic, less electromechanical than he was).

The marker in RL001  is a 
Spyder Imagine.  A 9V battery powers a circuit board that drives a solenoid 
that flicks the sear to fire the marker.  The trigger presses a SPST 
microswitch.  According to my digital multimeter the microswitch passes a 
constant 480 uA (0.48 milliamps) when closed and one contact is at ground 
level (i.e. it's a low-side switch).  I was surprised the current was so 
low, I guess it's driving a Darlington pair?

I soldered a servo-style lead to the IN, VRC, and adjacent GND pins on the 
MOSFET board, and soldered a tiny link over the VRC and VCC pads to power 
the board from the R/C interface.  I soldered a 2-position screw terminal 
block (with 0.1" pin spacing, very small!) to the LO and adjacent GND pins 
(on the "wrong" side because a surface-mount device was in the way on the 
"right" side).  The marker has a pair of wires soldered to the trigger 
microswitch contacts and I connected the other ends of the wires to the 
screw terminals, making sure the ground side was connected correctly (GND 
pin to ground side of switch).

When operational an indicator LED on the switch board blinks on briefly 
about once a second to indicate is has a signal.  When the "fire" signal is 
sent the LED blinks off briefly about once a second and the marker fires 
with the first blink.  The rate of fire (cycling the R/C signal to re-fire 
the marker) is "plenty fast" ... no specifics here because Bazooka Joe is a 
single-shot asset so rate of fire isn't an issue.

Conclusion:
I see at least 4 options for firing an electronic marker via R/C:

1. Ignore the electronics and use a servo with an arm or cam to 
mechanically move the trigger or the microswitch actuator.
Pros: Simple, cheap, proven.  You can see if it's working.
Cons: The servo and arm/cam need to be aligned correctly with the trigger - 
needs mechanical engineering.  Subject to wear-and-tear.

2. Use an R/C relay-based switch (examples include the PicoSwitch 
 and the Pololu 
RC Switch with Relay ).  I used the 
PicoSwitch previously and it worked fine (as long as the pulses weren't 
more than 500 ms either side of center, which shouldn't be a problem with 
typical R/C gear).
Pros: Very small, easy to connect (polarity not an issue), voltage/current 
not an issue with typical markers, clicking sound confirms operation.
Cons: Some soldering required for cheaper products (around $10), not for 
more expensive ones (around $20).  Needs electrical and/or mechanical 
engineering.

3. Use a FET-based switch as above.
Pros: Very small, LED shows status.
Cons: Must get polarity right when connecting, some soldering required. 
 Needs electrical engineering.

4. Given the low current I observed it wouldn't be a stretch to build a 
home-grown solution.  A Pololu RC Switch with Digital Output 
, or a microprocessor (PIC 
, 
PICAXE , Arduino , Raspberry 
Pi , etc) with a resistor or two and a BJT or 
FET should do the trick.  I'll look into this "someday".
Pros: Customizable (e.g. with an MPU you can activate based on certain 
signal characteristic/s).  Cheapish if the parts are lying around your junk 
box.
Cons: Much assembly required.  Needs electronic engineering.

All these solutions are on the order of $10 or less if you can do some of 
the work, $20 or so if you just want to plug it in and go.

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